Electric brake system

ABSTRACT

An electric brake system is disclosed. The electric brake system includes a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output corresponding to displacement of a brake pedal, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to the one or more wheel cylinders, a first hydraulic flow path configured to communicate with the first pressure chamber, a second hydraulic flow path configured to branch from the first hydraulic flow path, a third hydraulic flow path configured to branch from the first hydraulic flow path, a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path, a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path, a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively, and a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively.

This application claims the benefit of Korean Patent Application No.2015-0162415, filed on Nov. 19, 2015 in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to an electric brakesystem, and more particularly, to an electric brake system generating abraking force using an electrical signal corresponding to a displacementof a brake pedal.

2. Description of the Related Art

A brake system for braking is necessarily mounted on a vehicle, and avariety of systems for providing stronger and more stable braking havebeen proposed recently.

For example, there are brake systems including an anti-lock brake system(ABS) for preventing a wheel from sliding while braking, a braketraction control system (BTCS) for preventing a driving wheel fromslipping when a vehicle is unintentionally or intentionally accelerated,an electronic stability control (ESC) system for stably maintaining adriving state of a vehicle by combining an ABS with traction control tocontrol hydraulic pressure of a brake, and the like.

Generally, an electric brake system includes a hydraulic pressure supplydevice which receives a braking intent of a driver in the form of anelectrical signal from a pedal displacement sensor which sensesdisplacement of a brake pedal when the driver steps on the brake pedaland then supplies hydraulic pressure to a wheel cylinder.

An electric brake system provided with such a hydraulic pressure supplydevice is disclosed in European Registered Patent No. EP 2 520 473.According to the disclosure in that document, the hydraulic pressuresupply device is configured such that a motor is activated according toa pedal effort of a brake pedal to generate braking pressure. At thispoint, the braking pressure is generated by converting a rotationalforce of the motor into rectilinear movement to pressurize a piston.

PRIOR ART DOCUMENT

-   -   (Patent Document) European Registered Patent No. EP 2 520 473 A1        (Honda Motor Co., Ltd.), Nov. 7, 2012.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide anelectric brake system including a hydraulic pressure supply device thatis operated with double action.

Additional aspects of the disclosure will be set forth in part in thedescription which follows and, in part, will be obvious from thedescription, or may be learned by practice of the disclosure.

In accordance with one aspect of the present invention, there may beprovided an electric brake system, which comprises a hydraulic pressuresupply device configured to generate hydraulic pressure using a pistonwhich is operated by means of an electrical signal that is outputcorresponding to displacement of a brake pedal, and including a firstpressure chamber provided at one side of the piston movably accommodatedinside a cylinder block and connected to one or more wheel cylinders,and a second pressure chamber provided at the other side of the pistonand connected to the one or more wheel cylinders, a first hydraulic flowpath configured to communicate with the first pressure chamber, a secondhydraulic flow path configured to branch from the first hydraulic flowpath, a third hydraulic flow path configured to branch from the firsthydraulic flow path, a fourth hydraulic flow path configured tocommunicate with the second pressure chamber and connected to the thirdhydraulic flow path, a fifth hydraulic flow path configured tocommunicate the second hydraulic flow path with the third hydraulic flowpath, a first hydraulic circuit including first and second branchingflow paths which branch from the second hydraulic flow path and areconnected to two wheel cylinders, respectively, and a second hydrauliccircuit including third and fourth branching flow paths which branchfrom the third hydraulic flow path and are connected to two wheelcylinders, respectively.

Also, the electric brake system may further include a first controlvalve provided at the second hydraulic flow path and configured tocontrol an oil flow, a second control valve provided at the thirdhydraulic flow path and configured to control an oil flow, a thirdcontrol valve provided at the fourth hydraulic flow path and configuredto control an oil flow, and a circuit balance valve provided at thefifth hydraulic flow path and configured to control an oil flow.

Also, the first control valve may be configured with a check valveconfigured to allow an oil flow in a direction from the hydraulicpressure supply device toward the one or more wheel cylinders and blockan oil flow in a reverse direction, and the second and third controlvalves and the circuit balance valve may be configured with a solenoidvalve configured to control an oil flow between the hydraulic pressuresupply device and the one or more wheel cylinders bidirectionally.

Also, the first and third control valves may be configured with a checkvalve configured to allow an oil flow in a direction from the hydraulicpressure supply device toward the one or more wheel cylinders and blockan oil flow in a reverse direction, and the second control valve and thecircuit balance valve may be configured with a solenoid valve configuredto control an oil flow between the hydraulic pressure supply device andthe one or more wheel cylinders bidirectionally.

Also, the second and third control valves may be normally closed typevalves that are usually closed and are open when an opening signal isreceived.

Also, the circuit balance valve may be a normally closed type valve thatis usually closed and is open when an opening signal is received.

Also, the electric brake system may further include a sixth hydraulicflow path configured to communicate the second hydraulic flow path withthe fourth hydraulic flow path, and a fourth control valve provided atthe sixth hydraulic flow path and configured to control an oil flow.

Also, the fourth control valve may be provided with a check valveconfigured to allow an oil flow in a direction from the hydraulicpressure supply device toward the one or more wheel cylinders and blockan oil flow in a reverse direction.

Also, the electric brake system may further include a seventh hydraulicflow path configured to communicate the second hydraulic flow path withthe fifth hydraulic flow path, and a fifth control valve provided at theseventh hydraulic flow path and configured to control an oil flow.

Also, the fifth control valve may be provided with a solenoid valveconfigured to control an oil flow between the hydraulic pressure supplydevice and the one or more wheel cylinders bidirectionally.

Also, the fifth control valve may be a normally closed type valve thatis usually closed and is open when an opening signal is received.

Also, the circuit balance valve may be installed at the fifth hydraulicflow path between a position at which the fifth hydraulic flow path isconnected to the second hydraulic flow path and a position at which thefifth hydraulic flow path and the seventh hydraulic flow path areconnected to each other, and between a position at which the fifthhydraulic flow path is connected to the third hydraulic flow path andthe position at which the fifth hydraulic flow path and the seventhhydraulic flow path are connected to each other, based on a position atwhich the seventh hydraulic flow path is connected to the fifthhydraulic flow path.

Also, the electric brake system may further include a first dump flowpath configured to communicate with the first pressure chamber andconnected to a reservoir, a second dump flow path configured tocommunicate with the second pressure chamber and connected to thereservoir, a first dump valve provided at the first dump flow path,configured to control an oil flow, and configured with a check valveconfigured to allow an oil flow in a direction from the reservoir towardthe first pressure chamber and block an oil flow in a reverse direction,a second dump valve provided at the second dump flow path, configured tocontrol an oil flow, and configured with a check valve configured toallow an oil flow in a direction from the reservoir toward the secondpressure chamber and block an oil flow in a reverse direction, and athird dump valve provided at a bypass flow path connecting an upstreamside of the second dump valve to a downstream side thereof at the seconddump flow path, configured to control an oil flow, and configured with asolenoid valve configured to control an oil flow between the reservoirand the second pressure chamber bidirectionally.

Also, the third dump valve may be a normally opened type valve that isusually opened and is closed when a closing signal is received.

Also, the hydraulic pressure supply device may further include thecylinder block, the piston movably accommodated inside the cylinderblock and configured to perform reciprocal movement by means of arotational force of a motor, a first communicating hole formed at thecylinder block forming the first pressure chamber and configured tocommunicate with the first hydraulic flow path, and a secondcommunicating hole formed at the cylinder block forming the secondpressure chamber and configured to communicate with the fourth hydraulicflow path.

In accordance with another aspect of the present invention, there isprovided an electric brake system, which comprises a master cylinder atwhich first and second hydraulic ports are formed, connected to areservoir storing oil therein, configured with one or more pistons, andconfigured to discharge oil according to a pedal effort of a brakepedal, a pedal displacement sensor configured to sense displacement ofthe brake pedal, a hydraulic pressure supply device configured togenerate hydraulic pressure using a piston which is operated by means ofan electrical signal that is output from the pedal displacement sensor,and including a first pressure chamber provided at one side of thepiston movably accommodated inside a cylinder block and connected to oneor more wheel cylinders, and a second pressure chamber provided at theother side of the piston and connected to one or more wheel cylinders, afirst hydraulic flow path configured to communicate with the firstpressure chamber, a second hydraulic flow path configured to branch fromthe first hydraulic flow path, a third hydraulic flow path configured tobranch from the first hydraulic flow path, a fourth hydraulic flow pathconfigured to communicate with the second pressure chamber and connectedto the third hydraulic flow path, a fifth hydraulic flow path configuredto communicate the second hydraulic flow path with the third hydraulicflow path, a first hydraulic circuit including first and secondbranching flow paths which branch from the second hydraulic flow pathand are connected to two wheel cylinders, respectively, and first andsecond inlet valves configured to control the first and second branchingflow paths, respectively, a second hydraulic circuit including third andfourth branching flow paths which branch from the third hydraulic flowpath and are connected to two wheel cylinders, respectively, a firstbackup flow path configured to connect the first hydraulic port to thesecond hydraulic flow path, a second backup flow path configured toconnect the second hydraulic port to the third hydraulic flow path, afirst cut valve provided at the first backup flow path and configured tocontrol an oil flow, a second cut valve provided at the second backupflow path and configured to control an oil flow, and a simulation deviceprovided at a flow path branching from the first backup flow path,configured with a simulator valve provided at a flow path connecting asimulation chamber storing oil therein to the reservoir, and configuredto provide a reaction force according to a pedal effort of the brakepedal.

Also, the electric brake system may further include a first controlvalve provided at the second hydraulic flow path and configured tocontrol an oil flow, a second control valve provided at the thirdhydraulic flow path and configured to control an oil flow, a thirdcontrol valve provided at the fourth hydraulic flow path and configuredto control an oil flow, and a circuit balance valve provided at thefifth hydraulic flow path and configured to control an oil flow.

Also, the first backup flow path may be connected to a downstream sideof the first control valve at the second hydraulic flow path, and thesecond backup flow path is connected to a downstream side of the secondcontrol valve at the third hydraulic flow path.

Also, the electric brake system may include an electronic control unit(ECU) configured to control an operation of the motor, and opening andclosing of the second and third control valves, the circuit balancevalve, and first to fourth inlet valves on the basis of hydraulicpressure information and displacement information of the brake pedal.

Also, when an imbalance in pressure between the first pressure chamberand the second pressure chamber occurs, the ECU may open the secondcontrol valve and the third control valve to accomplish a balance inpressure between the first pressure chamber and the second pressurechamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system according to a first embodiment of thepresent disclosure.

FIG. 2 is an enlarged diagram illustrating a hydraulic pressure supplyunit according to the first embodiment of the present disclosure.

FIGS. 3 and 4 show a state in which the electric brake system accordingto the first embodiment of the present disclosure performs a brakingoperation normally, FIG. 3 is a hydraulic circuit diagram illustrating asituation in which braking pressure is provided while a hydraulic pistonis moved forward, and FIG. 4 is a hydraulic circuit diagram illustratinga situation in which the braking pressure is provided while thehydraulic piston is moved backward.

FIGS. 5 and 6 show a state in which the braking force is released whenthe electric brake system according to the first embodiment of thepresent disclosure operates normally, FIG. 5 is a hydraulic circuitdiagram illustrating a situation in which the braking pressure isreleased while the hydraulic piston is moved forward, and

FIG. 6 is a hydraulic circuit diagram illustrating a situation in whichthe braking pressure is released while the hydraulic piston is movedbackward.

FIGS. 7 and 8 show a state in which an anti-lock brake system (ABS) isoperated through the electric brake system according to the firstembodiment of the present disclosure, FIG. 7 is a hydraulic circuitdiagram illustrating a situation in which the hydraulic piston is movedforward and selective braking is performed, and FIG. 8 is a hydrauliccircuit diagram illustrating a situation in which the hydraulic pistonis moved backward and selective braking is performed.

FIG. 9 is a hydraulic circuit diagram illustrating a situation in whichthe electric brake system according to the first embodiment of thepresent disclosure operates abnormally.

FIG. 10 is a hydraulic circuit diagram illustrating a state in which theelectric brake system according to the first embodiment of the presentdisclosure operates in a dump mode.

FIG. 11 is a hydraulic circuit diagram illustrating a state in which theelectric brake system according to the first embodiment of the presentdisclosure operates in a balance mode.

FIG. 12 is a hydraulic circuit diagram illustrating a state in which theelectric brake system according to the first embodiment of the presentdisclosure operates in an inspection mode.

FIG. 13 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system according to a second embodiment of thepresent disclosure.

FIG. 14 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system according to a third embodiment of thepresent disclosure.

FIG. 15 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system according to a fourth embodiment of thepresent disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. The embodiments tobe described below are provided to fully convey the spirit of thepresent disclosure to a person skilled in the art. The presentdisclosure is not limited to the embodiments disclosed herein and may beimplemented in other forms. In the drawings, some portions not relatedto the description will be omitted and will not be shown in order toclearly describe the present disclosure, and also sizes of componentsmay be somewhat exaggerated to help understanding.

FIG. 1 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system 1 according to a first embodiment of thepresent disclosure.

Referring to FIG. 1, the electric brake system 1 generally includes amaster cylinder 20 for generating hydraulic pressure, a reservoir 30coupled to an upper part of the master cylinder 20 to store oil, aninput rod 12 for pressurizing the master cylinder 20 according to apedal effort of a brake pedal 10, a wheel cylinder 40 for receiving thehydraulic pressure to perform braking of each of wheels RR, RL, FR, andFL, a pedal displacement sensor 11 for sensing displacement of the brakepedal 10, and a simulation device 50 for providing a reaction forceaccording to the pedal effort of the brake pedal 10.

The master cylinder 20 may be configured to include at least one chamberto generate hydraulic pressure. As one example, the master cylinder 20may be configured to include two chambers, a first piston 21 a and asecond piston 22 a may be provided at the two chambers, respectively,and the first piston 21 a may be connected to the input rod 12. Further,the master cylinder 20 may include first and second hydraulic ports 24 aand 24 b which are formed thereon and through which hydraulic pressureis delivered from each of the two chambers.

Meanwhile, the master cylinder 20 may include two chambers to securesafety when one chamber fails. For example, one of the two chambers maybe connected to a front right wheel FR and a rear left wheel RL of avehicle, and the remaining chamber may be connected to a front leftwheel FL and a rear right wheel RR thereof. As described above, the twochambers may be independently configured so that braking of the vehiclemay be possible even when one of the two chambers fails.

Alternatively, unlike the drawing, one of the two chambers may beconnected to the two front wheels FR and FL and the remaining chambermay be connected to the two rear wheels RR and RL. In addition to thedescribed above, one of the two chambers may be connected to the frontleft wheel FL and the rear left wheel RL, and the remaining chamber maybe connected to the rear right wheel RR and the front right wheel FR. Inother words, a variety of connected configurations may be establishedbetween the chambers of the master cylinder 20 and the wheels.

Further, a first spring 21 b may be provided between the first piston 21a and the second piston 22 a of the master cylinder 20, and a secondspring 22 b may be provided between the second piston 22 a and an end ofthe master cylinder 20.

The first spring 21 b and the second spring 22 b are provided at the twochambers, respectively, to store an elastic force when the first piston21 a and the second piston 22 a are compressed according to a varianceof displacement of the brake pedal 10. Further, when a force pushing thefirst piston 21 a is less than the elastic force, the first spring 21 band the second spring 22 b may use the stored elastic force to push thefirst and second pistons 21 a and 22 a and return the first and secondpistons 21 a and 22 a to their original positions, respectively.

Meanwhile, the input rod 12 pressurizing the first piston 21 a of themaster cylinder 20 may come into close contact with the first piston 21a. In other words, there may be no gap between the master cylinder 20and the input rod 12. Consequently, when the brake pedal 10 is steppedon, the master cylinder 20 may be directly pressurized without a pedaldead stroke section.

The simulation device 50 may be connected to a first backup flow path251, which will be described below, to provide a reaction forceaccording to a pedal effort of the brake pedal 10. The reaction forcemay be provided to compensate for a pedal effort provided from a driversuch that a braking force may be finely controlled as intended by thedriver.

The simulation device 50 includes a simulation chamber 51 provided tostore oil flowing from the first hydraulic port 24 a of the mastercylinder 20, a reaction force piston 52 provided inside the simulationchamber 51, a pedal simulator provided with a reaction force spring 53elastically supporting the reaction force piston 52, and a simulatorvalve 54 connected to a rear end part of the simulation chamber 51.

The reaction force piston 52 and the reaction force spring 53 arerespectively installed to have a predetermined range of displacementwithin the simulation chamber 51 by means of oil flowing therein.

Meanwhile, the reaction force spring 53 shown in the drawing is merelyone embodiment capable of providing an elastic force to the reactionforce piston 52, and thus it may include numerous embodiments capable ofstoring the elastic force through shape deformation. As one example, thereaction force spring 53 includes a variety of members which areconfigured with a material including rubber and the like and have a coilor plate shape, thereby being able to store an elastic force.

The simulator valve 54 may be provided at a flow path connecting a rearend of the simulation chamber 51 to the reservoir 30. A front end of thesimulation chamber 51 may be connected to the master cylinder 20, andthe rear end of the simulation chamber 51 may be connected to thereservoir 30 through the simulator valve 54. Therefore, even when thereaction force piston 52 returns, oil inside the reservoir 30 may flowthrough the simulator valve 54 so that an inside of the simulationchamber 51 is entirely filled with the oil.

Meanwhile, a plurality of reservoirs 30 are shown in the drawing, andthe same reference number is assigned to each of the plurality ofreservoirs 30. These reservoirs may be configured with the samecomponents, and may alternatively be configured with differentcomponents. As one example, the reservoir 30 connected to the simulationdevice 50 may be the same as the reservoir 30 connected to the mastercylinder 20, or may be a storage part capable of storing oil inseparation from the reservoir 30 connected to the master cylinder 20.

Meanwhile, the simulator valve 54 may be configured with a normallyclosed type solenoid valve usually maintaining a closed state. When thedriver applies a pedal effort to the brake pedal 10, the simulator valve54 may be opened to deliver oil inside the simulation chamber 51 to thereservoir 30.

Also, a simulator check valve 55 may be installed to be connected inparallel with the simulator valve 54 between the pedal simulator and thereservoir 30. The simulator check valve 55 may allow the oil inside thereservoir 30 to flow toward the simulation chamber 51 and may block theoil inside the simulation chamber 51 from flowing toward the reservoir30 through a flow path at which the simulator check valve 55 isinstalled. When the pedal effort of the brake pedal 10 is released, theoil may be provided inside the simulation chamber 51 through thesimulator check valve 55 to ensure a rapid return of pressure of thepedal simulator.

To describe an operating process of the simulation device 50, when thedriver applies a pedal effort to the brake pedal 10, the oil inside thesimulation chamber 51, which is pushed by the reaction force piston 52of the pedal simulator while the reaction force piston 52 compresses thereaction force spring 53 and is delivered to the reservoir 30 throughthe simulator valve 54, and then a pedal feeling is provided to thedriver through such an operation. Further, when the driver releases thepedal effort from the brake pedal 10, the reaction force spring 53 maypush the reaction force piston 52 to return the reaction force piston 52to its original state, and the oil inside the reservoir 30 may flow intothe simulation chamber 51 through the flow path at which the simulatorvalve 54 is installed and the flow path at which the simulator checkvalve 55 is installed, thereby completely filling the inside of thesimulation chamber 51 with the oil.

As described above, because the inside of the simulation chamber 51 isin a state in which the oil is filled therein at all times, friction ofthe reaction force piston 52 is minimized when the simulation device 50is operated, and thus durability of the simulation device 50 may beimproved and also introduction of foreign materials from the outside maybe blocked.

The electric brake system 1 according to the first embodiment of thepresent disclosure may include a hydraulic pressure supply device 100which is mechanically operated by receiving a braking intent of thedriver in the form of an electrical signal from the pedal displacementsensor 11 measuring displacement of the brake pedal 10, a hydrauliccontrol unit 200 configured with first and second hydraulic circuits 201and 202, each of which is provided at two wheels, and controlling ahydraulic pressure flow delivered to the wheel cylinder 40 that isprovided at each of the wheels RR, RL, FR, and FL, a first cut valve 261provided at the first backup flow path 251 connecting the firsthydraulic port 24 a to the first hydraulic circuit 201 to control ahydraulic pressure flow, a second cut valve 262 provided at a secondbackup flow path 252 connecting the second hydraulic port 24 b to thesecond hydraulic circuit 202 to control a hydraulic pressure flow, andan electronic control unit (ECU) (not shown) controlling the hydraulicpressure supply device 100 and valves 54, 60, 221 a, 221 b, 221 c, 221d, 222 a, 222 b, 222 c, 222 d, 232, 233, 243, and 250 on the basis ofhydraulic pressure information and pedal displacement information.

The hydraulic pressure supply device 100 may include a hydraulicpressure supply unit 110 for providing oil pressure delivered to thewheel cylinder 40, a motor 120 for generating a rotational force inresponse to an electrical signal of the pedal displacement sensor 11,and a power conversion unit 130 for converting rotational movement ofthe motor 120 into rectilinear movement and transmitting the rectilinearmovement to the hydraulic pressure supply unit 110. Alternatively, thehydraulic pressure supply unit 110 may be operated by means of pressureprovided from a high pressure accumulator instead of a driving forcesupplied from the motor 120.

Next, the hydraulic pressure supply unit 110 according to the embodimentof the present disclosure will be described with reference to FIG. 2.FIG. 2 is an enlarged diagram illustrating the hydraulic pressure supplyunit 110 according to the embodiment of the present disclosure.

The hydraulic pressure supply unit 110 includes a cylinder block 111 inwhich a pressure chamber for receiving and storing oil therein isformed, a hydraulic piston 114 accommodated in the cylinder block 111, asealing member 115 (that is, 115 a and 115 b) provided between thehydraulic piston 114 and the cylinder block 111 to seal the pressurechamber, and a drive shaft 133 connected to a rear end of the hydraulicpiston 114 to deliver power output from the power conversion unit 130 tothe hydraulic piston 114.

The pressure chamber may include a first pressure chamber 112 located ata front side (in a forward movement direction, that is, a leftwarddirection of the drawing) of the hydraulic piston 114, and a secondpressure chamber 113 located at a rear side (in a backward movementdirection, that is, a rightward direction of the drawing) of thehydraulic piston 114. In other words, the first pressure chamber 112 iscomparted by means of the cylinder block 111 and a front end of thehydraulic piston 114 and is provided to have a volume that variesaccording to movement of the hydraulic piston 114, and the secondpressure chamber 113 is comparted by means of the cylinder block 111 andthe rear end of the hydraulic piston 114 and is provided to have avolume that varies according to the movement of the hydraulic piston114.

The first pressure chamber 112 is connected to a first hydraulic flowpath 211 through a first communicating hole 111 a formed at a front sideof the cylinder block 111.

The first hydraulic flow path 211 branches into a second hydraulic flowpath 212 and a third hydraulic flow path 213 and connects the firstpressure chamber 112 to the first and second hydraulic circuits 201 and202.

Further, the second pressure chamber 113 is connected to a fourthhydraulic flow path 214 through a second communicating hole 111 b formedat a rear side of the cylinder block 111. The fourth hydraulic flow path214 branches into the second hydraulic flow path 212 and the thirdhydraulic flow path 213 and connects the hydraulic pressure supply unit110 to the first hydraulic circuit 201 and the second hydraulic circuit202.

The sealing member 115 includes a piston sealing member 115 a providedbetween the hydraulic piston 114 and the cylinder block 111 to sealbetween the first pressure chamber 112 and the second pressure chamber113, and a drive shaft sealing member 115 b provided between the driveshaft 133 and the cylinder block 111 to seal openings of the secondpressure chamber 113 and the cylinder block 111. In other words,hydraulic pressure or negative pressure of the first pressure chamber112, which is generated while the hydraulic piston 114 is moved forwardor backward, may be blocked by the piston sealing member 115 a and maybe delivered to the first and fourth hydraulic flow paths 211 and 214without leaking into the second pressure chamber 113. Further, hydraulicpressure or negative pressure of the second pressure chamber 113, whichis generated while the hydraulic piston 114 is moved forward orbackward, may be blocked by the drive shaft sealing member 115 b and maynot leak into the cylinder block 111.

The first and second pressure chambers 112 and 113 may be respectivelyconnected to the reservoir 30 by means of dump flow paths 116 and 117,and receive and store oil supplied from the reservoir 30 or deliver oilinside the first or second pressure chamber 112 or 113 to the reservoir30. As one example, the dump flow paths 116 and 117 may include a firstdump flow path 116 branching from the first pressure chamber 112 andconnected to the reservoir 30, and a second dump flow path 117 branchingfrom the second pressure chamber 113 and connected to the reservoir 30.

Also, the first pressure chamber 112 may be connected to the first dumpflow path 116 through a third communicating hole 111 c formed at a frontside, and the second pressure chamber 113 may be connected to the seconddump flow path 117 through a fourth communicating hole 111 d formed at arear side.

Referring back to FIG. 1, flow paths 211, 212, 213, 214, 215, 216, and217, and valves 231, 232, 233, 234, 235, 236, 237, 241, 242, and 243,which are connected to the first pressure chamber 112 and the secondpressure chamber 113, will be described.

The first communicating hole 111 a communicating with the firsthydraulic flow path 211 and the third communicating hole 111 ccommunicating with the first dump flow path 116 may be formed at thefront side of the first pressure chamber 112. Further, the secondcommunicating hole 111 b communicating with the fourth hydraulic flowpath 214 and the fourth communicating hole 111 d communicating with thesecond dump flow path 117 may be formed at the second pressure chamber113.

The first hydraulic flow path 211 branches into the second hydraulicflow path 212 communicating with the first hydraulic circuit 201 and thethird hydraulic flow path 213 communicating with the second hydrauliccircuit 202. Therefore, hydraulic pressure may be delivered to both thefirst hydraulic circuit 201 and the second hydraulic circuit 202 whilethe hydraulic piston 114 is moved forward.

Also, the electric brake system 1 according to the first embodiment ofthe present disclosure may include a first control valve 231 and asecond control valve 232 which are provided at the second and thirdhydraulic flow paths 212 and 213, respectively, to control an oil flow.

Further, the first control valve 231 may be configured with a checkvalve that allows only an oil flow in a direction from the firstpressure chamber 112 toward the first hydraulic circuit 201 and blocksan oil flow in a reverse direction. That is, the first control valve 231may allow the hydraulic pressure of the first pressure chamber 112 to bedelivered to the first hydraulic circuit 201, and prevent the hydraulicpressure of the first hydraulic circuit 201 from leaking into the firstpressure chamber 112 through the second hydraulic flow path 212.

Further, the second control valve 232 may be configured with a solenoidvalve capable of bidirectionally controlling an oil flow of the thirdhydraulic flow path 213. That is, the second control valve 232 may allowthe hydraulic pressure of the first pressure chamber 112 to be deliveredto the second hydraulic circuit 202 when braking is performed, whereasit may allow hydraulic pressure of the second hydraulic circuit 202 tobe delivered to the first pressure chamber 112 through the thirdhydraulic flow path 213 when braking is released.

Also, the second control valve 232 may be configured with a normallyclosed type solenoid valve that is usually closed and is open when anopening signal is received from the ECU.

In addition, the fourth hydraulic flow path 214 may be provided tocommunicate the second pressure chamber 113 with the third hydraulicflow path 213.

Moreover, the electric brake system 1 according to the first embodimentof the present disclosure may be provided with a fifth hydraulic flowpath 215 communicating the first hydraulic circuit 201 and the secondhydraulic circuit 202. As one example, the fifth hydraulic flow path 215may be provided to communicate the second hydraulic flow path 212 withthe third hydraulic flow path 213, and in particular, one side of thefifth hydraulic flow path 215 may be connected to a downstream side ofthe first control valve 231 and the other side thereof may be connectedto a downstream side of the second control valve 232.

Also, the electric brake system 1 according to the first embodiment ofthe present disclosure may include a circuit balance valve 250 which isprovided at the fifth hydraulic flow path 215 communicating the firstpressure chamber 112 with the second pressure chamber 113 to control anoil flow. As one example, the circuit balance valve 250 may be installedat the fifth hydraulic flow path 215 communicating the second hydraulicflow path 212 with the third hydraulic flow path 213.

Further, the circuit balance valve 250 may be configured with a solenoidvalve capable of bidirectionally controlling an oil flow of the fifthhydraulic flow path 215. That is, the circuit balance valve 250 mayallow hydraulic pressure of the second hydraulic flow path 212 to bedelivered to the third hydraulic flow path 213 and also hydraulicpressure of the third hydraulic flow path 213 to be delivered to thesecond hydraulic flow path 212.

Also, the circuit balance valve 250 may be configured with a normallyclosed type solenoid valve that is usually closed and is open when anopening signal is received from the ECU.

Further, the second pressure chamber 113 may communicate with both thefirst hydraulic circuit 201 and the second hydraulic circuit 202. Thatis, the fourth hydraulic flow path 214 may be connected to the thirdhydraulic flow path 213 to communicate with the second hydraulic circuit202, and may communicate with the first hydraulic circuit 201 throughthe fifth hydraulic flow path 215 that branches from the third hydraulicflow path 213 and is connected to the second hydraulic flow path 212.Consequently, hydraulic pressure may be delivered to both the firsthydraulic circuit 201 and the second hydraulic circuit 202 while thehydraulic piston 114 is moved backward.

While the hydraulic piston 114 is moved backward, two operations may beperformed. First, using the negative pressure generated in the firstpressure chamber 112, the oil in the first and second hydraulic circuits201 and 202 may be returned to the first pressure chamber 112 to releasea braking force. Second, using the hydraulic pressure generated in thesecond pressure chamber 113, the oil in the second pressure chamber 113may be delivered to the first and second hydraulic circuits 201 and 202to apply a braking force.

The second control valve 232 and the third control valve 233 may controloil flows of the third hydraulic flow path 213 and the fourth hydraulicflow path 214, respectively, to enable a selection of the abovedescribed two operations. In other words, when the second control valve232 opens the third hydraulic flow path 213 and the third control valve233 blocks the fourth hydraulic flow path 214, the oil in the first andsecond hydraulic circuits 201 and 202 may be returned to the firstpressure chamber 112 to release a braking force. On the other hand, whenthe second control valve 232 blocks the third hydraulic flow path 213and the third control valve 233 opens the fourth hydraulic flow path214, the oil in the second pressure chamber 113 may be delivered to thefirst and second hydraulic circuits 201 and 202 to apply a brakingforce.

Also, the electric brake system 1 according to the first embodiment ofthe present disclosure may further include a first dump valve 241 and asecond dump valve 242 which are provided at the first and second dumpflow paths 116 and 117, respectively, and control an oil flow. The dumpvalves 241 and 242 may be a check valve that opens in a direction fromthe reservoir 30 to the first and second pressure chambers 112 and 113,and blocks in a reverse direction. That is, the first dump valve 241 maybe a check valve that allows oil to flow from the reservoir 30 to thefirst pressure chamber 112, and blocks the oil from flowing from thefirst pressure chamber 112 to the reservoir 30, and the second dumpvalve 242 may be a check valve that allows oil to flow from thereservoir 30 to the second pressure chamber 113, and blocks the oil fromflowing from the second pressure chamber 113 to the reservoir 30.

Also, the second dump flow path 117 may include a bypass flow path, anda third dump valve 243 may be installed at the bypass flow path tocontrol an oil flow between the second pressure chamber 113 and thereservoir 30.

The third dump valve 243 may be configured with a solenoid valve capableof bidirectionally controlling an oil flow, and with a normally opentype solenoid valve that is usually open and is closed when a closingsignal is received from the ECU.

The hydraulic pressure supply unit 110 of the electric brake system 1according to the first embodiment of the present disclosure may operatein double action. In other words, hydraulic pressure, which is generatedin the first pressure chamber 112 while the hydraulic piston 114 ismoved forward, may be delivered to the first hydraulic circuit 201through the first hydraulic flow path 211 and the second hydraulic flowpath 212 to operate the wheel cylinders 40 installed at the front rightwheel FR and the rear left wheel RL, and to the second hydraulic circuit202 through the first hydraulic flow path 211 and the third hydraulicflow path 213 to operate the wheel cylinders 40 installed at the rearright wheel RR and the front left wheel FL.

Similarly, hydraulic pressure, which is generated in the second pressurechamber 113 while the hydraulic piston 114 is moved backward, may bedelivered to the first hydraulic circuit 201 through the fourthhydraulic flow path 214 and the second hydraulic flow path 212 tooperate the wheel cylinders 40 installed at the front right wheel FR andthe rear left wheel RL, and to the second hydraulic circuit 202 throughthe fourth hydraulic flow path 214 and the third hydraulic flow path 213to operate the wheel cylinders 40 installed at the rear right wheel RRand the front left wheel FL.

Also, negative pressure, which is generated in the first pressurechamber 112 while the hydraulic piston 114 is moved backward, may causethe oil of the wheel cylinders 40 installed at the front right wheel FRand the rear left wheel RL to be suctioned and delivered to the firstpressure chamber 112 through the first hydraulic circuit 201 and thesecond hydraulic flow path 212, and may cause the oil of the wheelcylinders 40 installed at the rear right wheel RR and the front leftwheel FL to be suctioned and delivered to the first pressure chamber 112through the second hydraulic circuit 202 and the third hydraulic flowpath 213.

Meanwhile, the hydraulic pressure supply unit 110 operating with adouble action may discriminately use a low compression section and ahigh compression section. Also, a low decompression section and a highdecompression section may be discriminately used. Hereinafter, acompression situation in which the hydraulic pressure is delivered tothe wheel cylinders 40 will be described. However, the same principle isapplicable to a decompression situation in which the hydraulic pressureis discharged from the wheel cylinder 40.

While the hydraulic piston 114 is moved forward, the hydraulic pressureis generated in the first pressure chamber 112. Further, the more thehydraulic piston 114 is moved forward in an initial stage, the more anamount of oil delivered from the first pressure chamber 112 to the wheelcylinders 40 to increase braking pressure. However, because there is anactive stroke of the hydraulic piston 114, an increase of brakingpressure due to the forward movement of the hydraulic piston 114 islimited.

The hydraulic pressure supply unit 110 according to the first embodimentof the present disclosure may continuously increase the braking pressureusing the hydraulic piston 114 that is provided to be operable with adouble action even after the low compression section. That is, while thehydraulic piston 114 is again moved backward in a state in which thehydraulic piston 114 is maximally moved forward, the hydraulic pressureis generated in the second pressure chamber 113 and then it isadditionally provided to the wheel cylinders 40, thereby increasing thebraking pressure.

At this point, because negative pressure is generated in the firstpressure chamber 112 while the hydraulic piston 114 is moved backward,the hydraulic pressure of the wheel cylinders 40 should be preventedfrom being discharged due to such a negative pressure. For this purpose,the second control valve 232, which is operated to be open when thehydraulic pressure is discharged from the wheel cylinders 40, ismaintained in a closed state such that the hydraulic pressure of thewheel cylinders 40 may be prevented from being discharged through thethird hydraulic flow path 213. Meanwhile, because the first controlvalve 231 is configured with a check valve that allows only an oil flowin a direction from the first pressure chamber 112 to the secondhydraulic circuit 202, discharging of the hydraulic pressure of thewheel cylinders 40 through the second hydraulic flow path 212 is notallowed.

Meanwhile, an increase rate of pressure in a section in which thehydraulic piston 114 is moved forward to generate the hydraulic pressurein the first pressure chamber 112 may be different from that in asection in which the hydraulic piston 114 is moved backward to generatethe hydraulic pressure in the second pressure chamber 113. The reasonfor that is that a cross section of the hydraulic piston 114 in thesecond pressure chamber 113 is less than that of the hydraulic piston114 in the first pressure chamber 112 by a cross section of the driveshaft 133. As a cross section of the hydraulic piston 114 is small, anincrease and decrease rate of volume according to a stroke of thehydraulic piston 114 is reduced. Therefore, a volume per stroke distanceof the oil, which is pushed while the hydraulic piston 114 is movedbackward, in the second pressure chamber 113 is less than that of theoil, which is pushed while the hydraulic piston 114 is moved forward, inthe first pressure chamber 112.

Next, the motor 120 and the power conversion unit 130 of the hydraulicpressure supply device 100 will be described.

The motor 120 is a device for generating a rotational force according toa signal output from the ECU (not shown) and may generate the rotationalforce in a forward or backward direction. An angular velocity and arotational angle of the motor 120 may be precisely controlled. Becausesuch a motor 120 is generally known in the art, a detailed descriptionthereof will be omitted.

Meanwhile, the ECU controls not only the motor 120 but also valves 54,60, 221 a, 221 b, 221 c, 221 d, 222 a, 222 b, 222 c, 222 d, 232, 233,243, and 250 provided at the electric brake system 1 of the presentdisclosure, which will be described below. An operation of controlling aplurality of valves according to displacement of the brake pedal 10 willbe described below.

A driving force of the motor 120 generates displacement of the hydraulicpiston 114 through the power conversion unit 130, and hydraulicpressure, which is generated while the hydraulic piston 114 slidesinside the pressure chamber, is delivered to the wheel cylinder 40installed at each of the wheels RR, RL, FR, and FL through the first andsecond hydraulic flow paths 211 and 212.

The power conversion unit 130 is a device for converting a rotationalforce into rectilinear movement, and, as one example, may be configuredwith a worm shaft 131, a worm wheel 132, and the drive shaft 133.

The worm shaft 131 may be integrally formed with a rotational shaft ofthe motor 120, and rotates the worm wheel 132 engaged therewith andcoupled thereto through a worm that is formed on an outercircumferential surface of the worm shaft 131. The worm wheel 132linearly moves the drive shaft 133 engaged therewith and coupledthereto, and the drive shaft 133 is connected to the hydraulic piston114 to slide the hydraulic piston 114 inside the cylinder block 111.

To describe such operations again, a signal, which is sensed by thepedal displacement sensor 11 when displacement occurs at the brake pedal10, is transmitted to the ECU (not shown), and then the ECU drives themotor 120 in one direction to rotate the worm shaft 131 in the onedirection. A rotational force of the worm shaft 131 is transmitted tothe drive shaft 133 via the worm wheel 132, and then the hydraulicpiston 114 connected to the drive shaft 133 is moved forward to generatehydraulic pressure in the first pressure chamber 112.

On the other hand, when the pedal effort is released from the brakepedal 10, the ECU drives the motor 120 in a reverse direction, and thusthe worm shaft 131 is reversely rotated. Consequently, the worm wheel132 is also reversely rotated, and thus negative pressure is generatedin the first pressure chamber 112 while the hydraulic piston 114connected to the drive shaft 133 is returned to its original position,that is, moved backward.

Meanwhile, it is possible for the generation of hydraulic pressure andnegative pressure to be opposite to that which is described above. Thatis, the signal, which is sensed by the pedal displacement sensor 11 whenthe displacement occurs at the brake pedal 10, is transmitted to the ECU(not shown), and then the ECU drives the motor 120 in the reversedirection to reversely rotate the worm shaft 131. The rotational forceof the worm shaft 131 is transmitted to the drive shaft 133 via the wormwheel 132, and then the hydraulic piston 114 connected to the driveshaft 133 is moved backward to generate hydraulic pressure in the secondpressure chamber 113.

On the other hand, when the pedal effort is released from the brakepedal 10, the ECU drives the motor 120 in the one direction, and thusthe worm shaft 131 is rotated in the one direction. Consequently, theworm wheel 132 is also reversely rotated, and thus negative pressure isgenerated in the second pressure chamber 113 while the hydraulic piston114 connected to the drive shaft 133 is returned to its originalposition, that is, is moved forward.

As described above, the hydraulic pressure supply device 100 serves todeliver the hydraulic pressure to the wheel cylinders 40 or to cause thehydraulic pressure to be discharged therefrom and delivered to thereservoir 30 according to a rotational direction of the rotational forcegenerated from the motor 120.

Meanwhile, when the motor 120 is rotated in the one direction, thehydraulic pressure may be generated in the first pressure chamber 112 orthe negative pressure may be generated in the second pressure chamber113, and whether the hydraulic pressure is used for braking or thenegative pressure is used for releasing braking may be determinedthrough the control of the valves 54, 60, 221 a, 221 b, 221 c, 221 d,222 a, 222 b, 222 c, 222 d, 232, 233, 243, and 250. This will bedescribed in detail below.

Although not shown in the drawing, the power conversion unit 130 may beconfigured with a ball screw nut assembly. For example, the powerconversion unit 130 may be configured with a screw which is integrallyformed with the rotational shaft of the motor 120 or is connected to androtated with the rotational shaft thereof, and a ball nut which isscrew-coupled to the screw in a state in which rotation of the ball nutis restricted to perform rectilinear movement according to rotation ofthe screw. The hydraulic piston 114 is connected to the ball nut of thepower conversion unit 130 to pressurize the pressure chamber by means ofthe rectilinear movement of the ball nut. Such a ball screw nut assemblyis a device for converting rotational movement into rectilinearmovement, and a structure thereof is generally known in the art so thata detailed description thereof will be omitted.

Further, it should be understood that the power conversion unit 130according to one embodiment of the present disclosure may employ anystructure capable of converting a rotational movement into a rectilinearmovement in addition to the structure of the ball screw nut assembly.

Also, the electric brake system 1 according to the first embodiment ofthe present disclosure may further include the first and second backupflow paths 251 and 252 capable of directly supplying oil discharged fromthe master cylinder 20 to the wheel cylinders 40 when the hydraulicpressure supply device 100 operates abnormally.

The first cut valve 261 for controlling an oil flow may be provided atthe first backup flow path 251, and the second cut valve 262 forcontrolling an oil flow may be provided at the second backup flow path252. Also, the first backup flow path 251 may connect the firsthydraulic port 24 a to the first hydraulic circuit 201, and the secondbackup flow path 252 may connect the second hydraulic port 24 b to thesecond hydraulic circuit 202.

Further, the first and second cut valves 261 and 262 may be configuredwith a normally opened type solenoid valve that is usually open and isclosed when a closing signal is received from the ECU.

Next, the hydraulic control unit 200 according to the first embodimentof the present disclosure will be described with reference to FIG. 1.

The hydraulic control unit 200 may be configured with the firsthydraulic circuit 201 and the second hydraulic circuit 202, each ofwhich receives hydraulic pressure to control two wheels. As one example,the first hydraulic circuit 201 may control the front right wheel FR andthe rear left wheel RL, and the second hydraulic circuit 202 may controlthe front left wheel FL and the rear right wheel RR. Further, the wheelcylinder 40 is installed at each of the wheels FR, FL, RR, and RL toperform braking by receiving the hydraulic pressure.

The first hydraulic circuit 201 is connected to the first hydraulic flowpath 211 to receive the hydraulic pressure provided from the hydraulicpressure supply device 100, and the first hydraulic flow path 211branches into two flow paths that are connected to the front right wheelFR and the rear left wheel RL, respectively. Similarly, the secondhydraulic circuit 202 is connected to the second hydraulic flow path 212to receive the hydraulic pressure provided from the hydraulic pressuresupply device 100, and the second hydraulic flow path 212 branches intotwo flow paths that are connected to the front left wheel FL and therear right wheel RR, respectively.

The hydraulic circuits 201 and 202 may be provided with a plurality ofinlet valves 221 (that is, 221 a, 221 b, 221 c, and 221 d) to control ahydraulic pressure flow. As one example, two inlet valves 221 a and 221b may be provided at the first hydraulic circuit 201 and connected tothe first hydraulic flow path 211 to independently control the hydraulicpressure delivered to two of the wheel cylinders 40. Also, two inletvalves 221 c and 221 d may be provided at the second hydraulic circuit202 and connected to the second hydraulic flow path 212 to independentlycontrol the hydraulic pressure delivered to two of the wheel cylinders40.

Further, the plurality of inlet valves 221 may be disposed at anupstream side of each of the wheel cylinders 40 and may be configuredwith a normally opened type solenoid valve that is usually open and isclosed when a closing signal is received from the ECU.

Also, the hydraulic circuits 201 and 202 may include check valves 223 a,223 b, 223 c, and 223 d, each of which is provided at a bypass flow pathconnecting a front side to a rear side of each of the inlet valves 221a, 221 b, 221 c, and 221 d. Each of the check valves 223 a, 223 b, 223c, and 223 d may be provided to allow only an oil flow in a directionfrom the wheel cylinder 40 to the hydraulic pressure supply unit 110 andblock an oil flow in a direction from the hydraulic pressure supply unit110 to the wheel cylinder 40. Each of the check valves 223 a, 223 b, 223c, and 223 d may be operated to rapidly discharge braking pressure fromthe wheel cylinder 40, and to allow the hydraulic pressure of the wheelcylinder 40 to be delivered to hydraulic pressure supply unit 110 whenthe inlet valves 221 a, 221 b, 221 c, and 221 d are operated abnormally.

Also, the hydraulic circuits 201 and 202 may be further provided with aplurality of outlet valves 222 (that is, 222 a, 222 b, 222 c, and 222 d)connected to the reservoirs 30 to improve brake release performance whenthe brake is released. Each of the outlet valves 222 is connected to thewheel cylinder 40 to control discharging of the hydraulic pressure fromeach of the wheels RR, RL, FR, and FL. That is, when braking pressure ofeach of the wheels RR, RL, FR, and FL is measured and decompression ofthe brake is determined to be required, the outlet valves 222 may beselectively opened to control the braking pressure.

Further, the outlet valves 222 may be configured with normally closedtype solenoid valves that are usually closed and are open when anopening signal is received from the ECU.

In addition, the hydraulic control unit 200 may be connected to thebackup flow paths 251 and 252. As one example, the first hydrauliccircuit 201 may be connected to the first backup flow path 251 toreceive the hydraulic pressure provided from the master cylinder 20, andthe second hydraulic circuit 202 may be connected to the second backupflow path 252 to receive the hydraulic pressure provided from the mastercylinder 20. As one example, the first backup flow path 251 may beconnected to the second hydraulic flow path 212, and the second backupflow path 252 may be connected to the third hydraulic flow path 213.

At this point, the first backup flow path 251 may be connected to thefirst hydraulic circuit 201 at an upstream side of each of the first andsecond inlet valves 221 a and 221 b. Similarly, the second backup flowpath 252 may be connected to the second hydraulic circuit 202 at anupstream side of each of the third and fourth inlet valves 221 c and 221d. Consequently, when the first and second cut valves 261 and 262 areclosed, the hydraulic pressure provided from the hydraulic pressuresupply device 100 may be supplied to the wheel cylinders 40 through thefirst and second hydraulic circuits 201 and 202. Also, when the firstand second cut valves 261 and 262 are opened, the hydraulic pressureprovided from the master cylinder 20 may be supplied to the wheelcylinders 40 through the first and second backup flow paths 251 and 252.At this point, because the plurality of inlet valves 221 a, 221 b, 221c, and 221 d are in an opened state, there is no need to switch theiroperation states.

Meanwhile, an undescribed reference number “PS1” is a hydraulic flowpath pressure sensor which senses hydraulic pressure of each of thefirst and second hydraulic circuits 201 and 202, and an undescribedreference number “PS2” is a backup flow path pressure sensor whichsenses oil pressure of the master cylinder 20. Further, an undescribedreference number “MPS” is a motor control sensor which controls arotational angle or a current of the motor 120.

Hereinafter, an operation of the electric brake system 1 according tothe first embodiment of the present disclosure will be described indetail.

FIGS. 3 and 4 show a state in which the electric brake system 1according to the first embodiment of the present disclosure performs abraking operation normally, FIG. 3 is a hydraulic circuit diagramillustrating a situation in which braking pressure is provided while thehydraulic piston 114 is moved forward, and FIG. 4 is a hydraulic circuitdiagram illustrating a situation in which braking pressure is providedwhile the hydraulic piston 114 is moved backward.

When a driver begins braking, an amount of braking requested by thedriver may be sensed through the pedal displacement sensor 11 on thebasis of information including pressure put on the brake pedal 10 by thedriver, and the like. The ECU (not shown) receives an electrical signaloutput from the pedal displacement sensor 11 to drive the motor 120.

Also, the ECU may receive an amount of regenerative braking through thebackup flow path pressure sensor PS2 provided at an outlet side of themaster cylinder 20 and the hydraulic flow path pressure sensor PS1provided at the second hydraulic circuit 202, and may calculate anamount of braking friction based on a difference between the amount ofbraking requested by the driver and the amount of regenerative braking,thereby determining the magnitude of an increase or reduction ofpressure at the wheel cylinder 40.

Referring to FIG. 3, when the driver steps on the brake pedal 10 at aninitial stage of braking, the motor 120 is operated to rotate in onedirection, and a rotational force of the motor 120 is delivered to thehydraulic pressure supply unit 110 by means of the power conversion unit130, and thus the hydraulic pressure is generated in the first pressurechamber 112 while the hydraulic piston 114 of the hydraulic pressuresupply unit 110 is moved forward. The hydraulic pressure discharged fromthe hydraulic pressure supply unit 110 is delivered to the wheelcylinder 40 provided at each of the four wheels through the firsthydraulic circuit 201 and the second hydraulic circuit 202 to generate abraking force.

In particular, the hydraulic pressure provided from the first pressurechamber 112 is directly delivered to the wheel cylinders 40 provided atthe two wheels FR and RL through the first hydraulic flow path 211connected to the first communicating hole 111 a. At this point, thefirst and second inlet valves 221 a and 221 b, which are respectivelyinstalled at two flow paths branching from the first hydraulic flow path211, are provided in an opened state. Also, the first and second outletvalves 222 a and 222 b, which are respectively installed at flow pathswhich respectively branch from the two flow paths branching from thefirst hydraulic flow path 211, are maintained in a closed state toprevent the hydraulic pressure from leaking into the reservoirs 30.

Further, the hydraulic pressure provided from the first pressure chamber112 is directly delivered to the wheel cylinders 40 provided at the twowheels RR and FL through the first hydraulic flow path 211 and the thirdhydraulic flow path 213 connected to the first communicating hole 111 a.At this point, the third and fourth inlet valves 221 c and 221 d, whichare respectively installed at two flow paths branching from the thirdhydraulic flow path 213, are provided in an opened state. Also, thethird and fourth outlet valves 222 c and 222 d, which are respectivelyinstalled at flow paths which respectively branch from the two flowpaths branching from the third hydraulic flow path 213, are maintainedin the closed state to prevent the hydraulic pressure from leaking intothe reservoirs 30.

Also, the circuit balance valve 250 is switched to an opened state toopen the fifth hydraulic flow path 215 so that the first hydrauliccircuit 201 and the second hydraulic circuit 202 may communicate witheach other. Therefore, even when an abnormality occurs at the firstcontrol valve 231 and the second control valve 232, the hydraulicpressure may be delivered to the first and second hydraulic circuits 201and 202 to ensure stable braking.

In addition, when the pressure delivered to the wheel cylinders 40 ismeasured as being higher than a target pressure value according to thepedal effort of the brake pedal 10, one or more among the first tofourth outlet valves 222 may be opened to control the pressure toconverge on the target pressure value.

Further, when the hydraulic pressure is generated in the hydraulicpressure supply device 100, the first and second cut valves 261 and 262installed at the first and second backup flow paths 251 and 252, whichare connected to the first and second hydraulic ports 24 a and 24 b ofthe master cylinder 20, are closed, and thus the hydraulic pressuredischarged from the master cylinder 20 is not delivered to the wheelcylinders 40.

Moreover, the pressure generated by means of pressurization of themaster cylinder 20 according to the pedal effort of the brake pedal 10is delivered to the simulation device 50 connected to the mastercylinder 20. At this point, the normally closed type simulator valve 54arranged at the rear end of the simulation chamber 51 is opened so thatthe oil filled in the simulation chamber 51 is delivered to thereservoir 30 through the simulator valve 54. Also, the reaction forcepiston 52 is moved, and pressure corresponding to a reaction force ofthe reaction force spring 53 supporting the reaction force piston 52 isgenerated inside the simulation chamber 51 to provide an appropriatepedal feeling to the driver.

Also, the hydraulic flow path pressure sensor PS1 installed at thesecond hydraulic flow path 212 may detect a flow rate delivered to thewheel cylinder 40 installed at the front left wheel FL or the rear rightwheel RR (hereinafter, simply referred to as the wheel cylinder 40).Therefore, the hydraulic pressure supply device 100 may be controlledaccording to an output of the hydraulic flow path pressure sensor PS1 tocontrol a flow rate delivered to the wheel cylinder 40. In particular, adistance and a speed of the forward movement of the hydraulic piston 114may be adjusted so that a flow rate discharged from the wheel cylinder40 and a discharge speed thereof may be controlled.

Unlike FIG. 3, even when the hydraulic piston 114 is moved in a reversedirection, that is, moved backward, a braking force may be generated atthe wheel cylinders 40.

Referring to FIG. 4, when the driver steps on the brake pedal 10 at aninitial stage of braking, the motor 120 is operated to rotate in thereverse direction, and a rotational force of the motor 120 is deliveredto the hydraulic pressure supply unit 110 by means of the powerconversion unit 130, and thus the hydraulic pressure is generated in thesecond pressure chamber 113 while the hydraulic piston 114 of thehydraulic pressure supply unit 110 is moved backward. The hydraulicpressure discharged from the hydraulic pressure supply unit 110 isdelivered to the wheel cylinder 40 provided at each of the four wheelsthrough the first hydraulic circuit 201 and the second hydraulic circuit202 to generate a braking force.

At this point, because the fourth hydraulic flow path 214 communicatingwith the second pressure chamber 113 is connected to the third hydraulicflow path 213, the third hydraulic flow path 213 connected to the secondhydraulic circuit 202 and the second hydraulic flow path 212 should beconnected to each other to deliver the hydraulic pressure to the secondhydraulic circuit 202. As one example, the circuit balance valve 250 maybe switched to an opened state, and thus the third hydraulic flow path213 may communicate with the second hydraulic flow path 212.

In particular, the hydraulic pressure provided from the second pressurechamber 113 is directly delivered to the wheel cylinders 40 provided atthe two wheels FR and RL through the fourth hydraulic flow path 214, thethird hydraulic flow path 213, the fifth hydraulic flow path 215, andthe second hydraulic flow path 212 which are connected to the secondcommunicating hole 111 b, and to the wheel cylinders 40 provided at thetwo wheels RR and FL through the fourth hydraulic flow path 214 and thethird hydraulic flow path 213.

Alternatively, when the second control valve 232 is switched to anopened state, the hydraulic pressure supplied from the second pressurechamber 113 may be directly delivered to the wheel cylinders 40, whichare provided at the two wheels FR and RL, connected from the secondhydraulic flow path 212 to the third hydraulic flow path 213 through thesecond control valve 232

Next, a case of releasing the braking force in the braking stateestablished when the electric brake system 1 according to the firstembodiment of the present disclosure operates normally will bedescribed.

FIG. 5 shows a state in which the braking force is released when theelectric brake system 1 according to the first embodiment of the presentdisclosure operates normally, and it is a hydraulic circuit diagramillustrating a situation in which braking pressure is released while thehydraulic piston 114 is moved backward

Referring to FIG. 5, when a pedal effort applied to the brake pedal 10is released, the motor 120 generates a rotational force in a reversedirection compared to that when the braking operation is performed todeliver the generated rotational force to the power conversion unit 130,and the worm shaft 131 of the power conversion unit 130, the worm wheel132 thereof, and the drive shaft 133 thereof are rotated in a reversedirection compared to that when the braking operation is performed tomove backward and return the hydraulic piston 114 to its originalposition, thereby releasing the pressure of the first pressure chamber112 or generating negative pressure therein. Further, the hydraulicpressure supply unit 110 receives the hydraulic pressure discharged fromthe wheel cylinders 40 through the first and second hydraulic circuits201 and 202 to deliver the received hydraulic pressure to the firstpressure chamber 112.

In particular, the negative pressure generated in the first pressurechamber 112 releases the pressure of the wheel cylinders 40 provided atthe two wheels FR and RL through the first hydraulic flow path 211 andthe second hydraulic flow path 212 connected to the first communicatinghole 111 a. At this point, the first and second inlet valves 221 a and221 b, which are respectively installed at the two flow paths branchingfrom the second hydraulic flow path 212, are provided in the openedstate. Also, the first and the second outlet valves 222 a and 222 b,which are respectively installed at flow paths that respectively branchfrom the two flow paths branching from the second hydraulic flow path212, are maintained in the closed state to prevent the oil of thereservoirs 30 from flowing into the second hydraulic flow path 212.

Meanwhile, the first control valve 231 installed at the second hydraulicflow path 212 is a check valve that blocks an oil flow flowing into thefirst pressure chamber 112 through the second hydraulic flow path 212.Consequently, the oil flowing from the first hydraulic circuit 201should bypass the first control valve 231 to move to the first pressurechamber 112.

For this purpose, the second control valve 232 and the circuit balancevalve 250 are switched to an opened state. As a result, the oildischarged from the wheel cylinders 40, which are provided at the twowheels FR and RL of the first hydraulic circuit 201, flows into thefirst pressure chamber 112 through the fifth hydraulic flow path 215,the third hydraulic flow path 213, and the first hydraulic flow path211.

Further, the negative pressure generated in the first pressure chamber112 releases the pressure of the wheel cylinders 40 provided at the twowheels FL and RR through the first hydraulic flow path 211 and the thirdhydraulic flow path 213 connected to the first communicating hole 111 a.At this point, the third and fourth inlet valves 221 c and 221 d, whichare respectively installed at the two flow paths branching from thethird hydraulic flow path 213, are provided in an opened state. Also,the third and fourth outlet valves 222 c and 222 d, which arerespectively installed at flow paths that respectively branch from thetwo flow paths branching from the second hydraulic flow path 212, aremaintained in the closed state to prevent the oil of the reservoirs 30from flowing into the second hydraulic flow path 212.

Also, when the negative pressure delivered to the first and secondhydraulic circuits 201 and 202 is measured as being higher than a targetpressure releasing value according to an amount of release of the brakepedal 10, one or more among the first to fourth outlet valves 222 may beopened to control the negative pressure to converge on the targetpressure releasing value.

In addition, when the hydraulic pressure is generated in the hydraulicpressure supply device 100, the first and second cut valves 261 and 262installed at the first and second backup flow paths 251 and 252, whichare connected to the first and second hydraulic ports 24 a and 24 b ofthe master cylinder 20, are closed so that the negative pressuregenerated in the master cylinder 20 is not delivered to the wheelcylinders 40.

Moreover, the hydraulic flow path pressure sensor PS1 installed at thesecond hydraulic flow path 212 may detect a flow rate discharged fromthe wheel cylinder 40 installed at the front left wheel FL or the rearright wheel RR. Therefore, the hydraulic pressure supply device 100 maybe controlled according to an output of the hydraulic flow path pressuresensor PS1 so that a flow rate discharged from the wheel cylinder 40 maybe controlled. In particular, a distance and a speed of the forwardmovement of the hydraulic piston 114 may be adjusted so that a flow ratedischarged from the wheel cylinder 40 and a discharge speed thereof maybe controlled.

Meanwhile, even when the hydraulic piston 114 is moved in a reversedirection, that is, moved forward, a braking force may be generated atthe wheel cylinder 40.

Referring to FIG. 6, when a pedal effort applied to the brake pedal 10is released, the motor 120 generates a rotational force in a reversedirection compared to that when performing the braking operation todeliver the generated rotational force to the power conversion unit 130,and the worm shaft 131 of the power conversion unit 130, the worm wheel132 thereof, and the drive shaft 133 thereof are rotated in a reversedirection compared to that when performing the braking operation to moveforward and return the hydraulic piston 114 to its original position,thereby releasing the pressure of the second pressure chamber 113 orgenerating negative pressure therein. Further, the hydraulic pressuresupply unit 110 receives the hydraulic pressure discharged from thewheel cylinders 40 through the first and second hydraulic circuits 201and 202 to deliver the received hydraulic pressure to the secondpressure chamber 113.

The second hydraulic flow path 212, which is connected to the firsthydraulic circuit 201, is connected to the fourth hydraulic flow path214 through the fifth hydraulic flow path 215 and the third hydraulicflow path 213, and the first and second inlet valves 221 a and 221 b,which are respectively installed at the two flow paths branching fromthe second hydraulic flow path 212, are provided in an opened state.Also, the first and second outlet valves 222 a and 222 b, which arerespectively installed at flow paths that branch from the secondhydraulic flow path 212, are maintained in the closed state to preventthe oil of the reservoirs 30 from flowing into the second hydraulic flowpath 212.

In particular, the negative pressure generated in the second pressurechamber 113 releases the pressure of the wheel cylinders 40 provided atthe two wheels FR and RL through the fourth hydraulic flow path 214connected to the second communicating hole 111 b. At this point, becausethe first control valve 231 is configured with a check valve that blocksan oil flow flowing into the first pressure chamber 112 through thesecond hydraulic flow path 212, the oil flowing from the first hydrauliccircuit 201 should bypass the first control valve 231.

For this purpose, the circuit balance valve 250 is switched to an openedstate. Therefore, the oil discharged from the wheel cylinders 40, whichare provided at the two wheels FR and RL of the first hydraulic circuit201, flows into the second pressure chamber 113 through the fifthhydraulic flow path 215 and the fourth hydraulic flow path 214.

Further, the negative pressure generated in the second pressure chamber113 releases the pressure of the wheel cylinders 40 provided at the twowheels FL and RR through the fourth hydraulic flow path 214 and thethird hydraulic flow path 213 which are connected to the secondcommunicating hole 111 b. At this point, the third and fourth inletvalves 221 c and 221 d, which are respectively installed at the two flowpaths branching from the third hydraulic flow path 213, are provided inan opened state. Also, the third and fourth outlet valves 222 c and 222d, which are respectively installed at flow paths that branch from thesecond hydraulic flow path 212, are maintained in the closed state toprevent the oil of the reservoirs 30 from flowing into the secondhydraulic flow path 212.

FIGS. 7 and 8 show a state in which an anti-lock brake system (ABS) isoperated through the electric brake system 1 according to the firstembodiment of the present disclosure, FIG. 7 is a hydraulic circuitdiagram illustrating a situation in which the hydraulic piston 114 ismoved forward and selective braking is performed, and FIG. 8 is ahydraulic circuit diagram illustrating a situation in which thehydraulic piston 114 is moved backward and selective braking isperformed.

When the motor 120 is operated according to a pedal effort of the brakepedal 10, a rotational force of the motor 120 is transmitted to thehydraulic pressure supply unit 110 through the power conversion unit130, thereby generating hydraulic pressure. At this point, the first andsecond cut valves 261 and 262 are closed and thus the hydraulic pressuredischarged from the master cylinder 20 is not delivered to the wheelcylinders 40.

Referring to FIG. 7, because hydraulic pressure is generated in thefirst pressure chamber 112 while the hydraulic piston 114 is movedforward and the fourth inlet valve 221 d is provided in the openedstate, the hydraulic pressure delivered through the third hydraulic flowpath 213 operates the wheel cylinder 40 located at the front left wheelFL to generate a braking force.

At this point, the second control valve 232 is switched to an openedstate. Further, the first to third inlet valves 221 a, 221 b, and 221 care switched to a closed state, and the first to fourth outlet valves222 a, 222 b, 222 c, and 222 d are maintained in the closed state.Moreover, the third dump valve 243 is provided in an opened state, andthus the second pressure chamber 113 is filled with the oil flowing fromthe reservoir 30.

Referring to FIG. 8, because hydraulic pressure is generated in thesecond pressure chamber 113 while the hydraulic piston 114 is movedbackward and the first inlet valve 221 a is provided in the openedstate, the hydraulic pressure delivered through the fourth hydraulicflow path 214 and the fifth hydraulic flow path 215 operates the wheelcylinder 40 located at the front right wheel FR to generate a brakingforce.

At this point, the third control valve 233 and the circuit balance valve250 are switched to an opened state. Further, the second to fourth inletvalves 221 b, 221 c, and 221 d are switched to the closed state, and thefirst to fourth outlet valves 222 a, 222 b, 222 c, and 222 d aremaintained in the closed state.

That is, the electric brake system 1 according to the first embodimentof the present disclosure may independently control operations of themotor 120 and each of the valves 54, 60, 221 a, 221 b, 221 c, 221 d, 222a, 222 b, 222 c, 222 d, 232, 233, 243, and 250 to selectively deliver ordischarge the hydraulic pressure to or from the wheel cylinder 40 ofeach of the wheels RL, RR, FL, and FR according to a required pressuresuch that a precise control of the hydraulic pressure may be possible.

Next, a case in which such an electric brake system 1 operatesabnormally will be described. FIG. 9 is a hydraulic circuit diagramillustrating a situation in which the electric brake system 1 accordingto the first embodiment of the present disclosure operates abnormally.

Referring to FIG. 9, when the electric brake system 1 operatesabnormally, each of the valves 54, 60, 221 a, 221 b, 221 c, 221 d, 222a, 222 b, 222 c, 222 d, 232, 233, 243, and 250 is provided in an initialstate of braking, that is, a non-operating state.

When a driver pressurizes the brake pedal 10, the input rod 12 connectedto the brake pedal 10 is moved forward, and the first piston 21 a, whichis in contact with the input rod 12, is moved forward and at the sametime the second piston 22 a is moved forward by means of thepressurization or movement of the first piston 21 a. At this point,because there is no gap between the input rod 12 and the first piston 21a, the braking may be rapidly performed.

Further, the hydraulic pressure discharged from the master cylinder 20is delivered to the wheel cylinders 40 through the first and secondbackup flow paths 251 and 252 that are connected for the purpose ofbackup braking to realize a braking force.

At this point, the first and second cut valves 261 and 262 respectivelyinstalled at the first and second backup flow paths 251 and 252, and theinlet valves 221 opening and closing the flow paths of the firsthydraulic circuit 201 and the second hydraulic circuit 202 areconfigured with normally opened type solenoid valves, and the simulatorvalve 54 and the outlet valves 222 are configured with normally closedtype solenoid valves so that the hydraulic pressure is directlydelivered to the four wheel cylinders 40. Therefore, braking is stablyrealized to improve braking safety.

FIG. 10 is a hydraulic circuit diagram illustrating a state in which theelectric brake system 1 according to the first embodiment of the presentdisclosure operates in a dump mode.

The electric brake system 1 according to the first embodiment of thepresent disclosure may discharge only braking pressure provided tocorresponding wheel cylinders 40 through the first to fourth outletvalves 222 a, 222 b, 222 c, and 222 d.

Referring to FIG. 10, when the first to fourth inlet valves 221 a, 221b, 221 c, and 221 d are switched to the closed state, the first to thirdoutlet valves 222 a, 222 b, and 222 c are maintained in the closedstate, and the fourth outlet valve 222 d is switched to the openedstate, the hydraulic pressure discharged from the wheel cylinder 40installed at the front left wheel FL is discharged to the reservoir 30through the fourth outlet valve 222 d.

The reason for that the hydraulic pressure in the wheel cylinders 40 isdischarged through the outlet valves 222 is that pressure in thereservoir 30 is less than that in the wheel cylinder 40. Generally, thepressure in the reservoir 30 is provided as atmospheric pressure.Because the pressure in the wheel cylinder 40 is generally andconsiderably higher than atmospheric pressure, the hydraulic pressure ofthe wheel cylinders 40 may be rapidly discharged to the reservoirs 30when the outlet valves 222 are opened.

Meanwhile, although not shown in the drawing, the fourth outlet valve222 d is opened to discharge the hydraulic pressure of the correspondingwheel cylinder 40 and at the same time the first to third inlet valves221 a, 221 b, and 221 c are maintained in the opened state so that thehydraulic pressure may be supplied to the three remaining wheels FR, RL,and RR.

Further, a flow rate discharged from the wheel cylinder 40 is increasedwhen a difference in pressure between the wheel cylinder 40 and thefirst pressure chamber 112 is large. As one example, as a volume of thefirst pressure chamber 112 is increased while the hydraulic piston 114is moved backward, a larger amount of flow rate may be discharged fromthe wheel cylinder 40.

As described above, each of the valves 221 a, 221 b, 221 c, 221 d, 222a, 222 b, 222 c, 222 d, 232, 233, 243, and 250 of the hydraulic controlunit 200 may be independently controlled to selectively deliver ordischarge the hydraulic pressure to or from the wheel cylinder 40 ofeach of the wheels RL, RR, FL, and FR according to a required pressuresuch that a precise control of the hydraulic pressure may be possible.

FIG. 11 is a hydraulic circuit diagram illustrating a state in which theelectric brake system 1 according to the first embodiment of the presentdisclosure operates in a balance mode.

Generally, a balance in pressure between the first pressure chamber 112and the second pressure chamber 113 is maintained. As one example, undera braking situation in which the hydraulic piston 114 is moved forwardto apply a braking force, only hydraulic pressure of the first pressurechamber 112 of the two pressure chambers is delivered to the wheelcylinders 40. However, in such a situation, because the oil in thereservoir 30 is delivered to the second pressure chamber 113 through thesecond dump flow path 117, a balance in pressure between the twopressure chambers is still maintained. On the other hand, under abraking situation in which the hydraulic piston 114 is moved backward toapply a braking force, only hydraulic pressure of the second pressurechamber 113 of the two pressure chambers is delivered to the wheelcylinders 40. However, even in such a situation, because the oil in thereservoir 30 is delivered to the first pressure chamber 112 through thefirst dump flow path 116, a balance in pressure between the two pressurechambers is still maintained.

However, when a leak occurs due to a repetitive operation of thehydraulic pressure supply device 100 or an ABS operation is abruptlyperformed, an imbalance in pressure between the first pressure chamber112 and the second pressure chamber 113 may be caused. That is, thehydraulic piston 114 may not be located at a calculated position tocause an incorrect operation.

In such a situation, the first hydraulic flow path 211 and the fourthhydraulic flow path 214 are connected to each other such that the firstpressure chamber 112 and the second pressure chamber 113 communicatewith each other. Therefore, a balance in pressure between the firstpressure chamber 112 and the second pressure chamber 113 is caused. Atthis point, to promote the balancing process, the motor 120 may beoperated to move the hydraulic piston 114 forward or backward.

The balance mode is performed when an imbalance in pressure between thefirst pressure chamber 112 and the second pressure chamber 113 occurs.As one example, the ECU may sense an imbalance state in pressure bydetecting the hydraulic pressure of the first hydraulic circuit 201 andthe hydraulic pressure of the second hydraulic circuit 202 from thehydraulic flow path pressure sensor PS1.

In the balance mode, the first pressure chamber 112 and the secondpressure chamber 113 communicate with each other. As one example, thesecond control valve 232 and the third control valve 233 are switched toan opened state, and thus the first hydraulic flow path 211, the thirdhydraulic flow path 213, and the fourth hydraulic flow path 214 may beconnected to each other. Thus, with only communication of the firsthydraulic flow path 211 and the fourth hydraulic flow path 214, abalance in pressure between the first pressure chamber 112 and thesecond pressure chamber 113 may be accomplished. To promote a balancingprocess, however, the hydraulic pressure supply device 100 may operate.

Hereinafter, an example when pressure in the first pressure chamber 112is greater than that in the second pressure chamber 113 will bedescribed. When the motor 120 is operated, the hydraulic piston 114 ismoved forward, the hydraulic pressure in the first pressure chamber 112is delivered from the first hydraulic flow path 211 to the fourthhydraulic flow path 214 through the second control valve 232 and thethird control valve 233 which are in the opened state, and during thisprocess, a balance in pressure between the first pressure chamber 112and the second pressure chamber 113 is accomplished.

When the pressure in the second pressure chamber 113 is greater thanthat in the first pressure chamber 112, the hydraulic pressure in thesecond pressure chamber 113 is delivered to the first pressure chamber112 to balance pressure.

FIG. 12 is a hydraulic circuit diagram illustrating a state in which theelectric brake system 1 according to the first embodiment of the presentdisclosure operates in an inspection mode.

As shown in FIG. 12, when the electric brake system 1 operatesabnormally, the valves 54, 60, 221 a, 221 b, 221 c, 221 d, 222 a, 222 b,222 c, 222 d, 232, 233, 243, and 250 are provided in an initial state ofbraking, that is, a non-operating state, and the first and second cutvalves 261 and 262 respectively installed at the first and second backupflow paths 251 and 252 and each of the inlet valves 221 provided at theupstream of the wheel cylinder 40 that is provided at each of the wheelsRR, RL, FR, and FL are opened so that the hydraulic pressure is directlydelivered to the wheel cylinders 40.

At this point, the simulator valve 54 is provided in the closed state sothat the hydraulic pressure delivered to the wheel cylinders 40 throughthe first backup flow path 251 is prevented from leaking into thereservoir 30 through the simulation device 50. Therefore, the driversteps on the brake pedal 10 so that the hydraulic pressure dischargedfrom the master cylinder 20 is delivered to the wheel cylinders 40without a loss to ensure stable braking.

However, when a leak occurs at the simulator valve 54, a portion of thehydraulic pressure discharged from the master cylinder 20 may be lost tothe reservoir 30 through the simulator valve 54. The simulator valve 54is provided to be closed in an abnormal mode, and the hydraulic pressuredischarged from the master cylinder 20 pushes the reaction force piston52 of the simulation device 50 so that a leak may occur at the simulatorvalve 54 by means of pressure formed at the rear end of the simulationchamber 51.

Therefore, when the leak occurs at the simulator valve 54, a brakingforce may not be obtained as intended by the driver. Consequently, thereis a problem in safety of braking.

The inspection mode is a mode in which it is inspected whether there isa loss of pressure by generating hydraulic pressure at the hydraulicpressure supply device 100 to inspect whether a leak occurs in thesimulator valve 54. When the hydraulic pressure discharged from thehydraulic pressure supply device 100 is delivered to the reservoir 30and causes a loss of pressure, it is difficult to verify whether a leakoccurs at the simulator valve 54.

Therefore, in the inspection mode, an inspection valve 60 may be closedand thus a hydraulic circuit connected to the hydraulic pressure supplydevice 100 may be configured as a closed circuit. That is, theinspection valve 60, the simulator valve 54, and the outlet valves 222are closed and thus the flow paths connecting the hydraulic pressuresupply device 100 to the reservoirs 30 are closed so that the closedcircuit may be configured.

In the inspection mode, the electric brake system 1 according to thefirst embodiment of the present disclosure may provide the hydraulicpressure to only the first backup flow path 251, which is connected tothe simulation device 50, of the first and second backup flow paths 251and 252. Therefore, to prevent the hydraulic pressure discharged fromthe hydraulic pressure supply device 100 from being delivered to themaster cylinder 20 through the second backup flow path 252, the secondcut valve 262 may be switched to a closed state and the circuit balancevalve 250 may be maintained in the closed state in the inspection mode.

Referring to FIG. 12, in the inspection mode, at an initial state ofeach of the valves 54, 60, 221 a, 221 b, 221 c, 221 d, 222 a, 222 b, 222c, 222 d, 232, 233, 243, and 250 provided at the electric brake system 1of the present disclosure, the first to fourth inlet valves 221 a, 221b, 221 c, and 221 d and the second cut valve 262 may be switched to theclosed state, and the first cut valve 261 is maintained in the openedstate so that the hydraulic pressure generated at the hydraulic pressuresupply device 100 may be delivered to the master cylinder 20. The inletvalves 221 are closed so that the hydraulic pressure of the hydraulicpressure supply device 100 may be prevented from being delivered to thefirst and second hydraulic circuits 201 and 202, the second cut valve262 is switched to the closed state so that the hydraulic pressure ofthe hydraulic pressure supply device 100 may be prevented fromcirculating along the first backup flow path 251 and the second backupflow path 252, and the inspection valve 60 is switched to a closed stateso that the hydraulic pressure supplied to the master cylinder 20 may beprevented from leaking into the reservoir 30.

Also, even when the second control valve 232 and the circuit balancevalve 250 are not switched to an opened state, the inspection mode maybe performed. The reason for that is that the hydraulic pressuregenerated in the first pressure chamber 112 may flow into the firstbackup flow path 251 through the first control valve 231 provided at thesecond hydraulic flow path 212. Further, because the second controlvalve 232 and the circuit balance valve 250 are maintained in the closedstate, a case in which a leak occurs at the second control valve 232 andthe circuit balance valve 250 may be detected.

In the inspection mode, after generating the hydraulic pressure at thehydraulic pressure supply device 100, the ECU may analyze a signaltransmitted from the backup flow path pressure sensor PS2 measuring oilpressure of the master cylinder 20 to sense whether a leak occurs at thesimulator valve 54. As one example, when there is no loss on the basisof the measurement result of the backup flow path pressure sensor PS2,the simulator valve 54 may be determined to have no leak, and when theloss occurs, the simulator valve 54 may be determined to have a leak.

FIG. 13 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system 2 according to a second embodiment of thepresent disclosure.

Comparing FIG. 1 with FIG. 13, a third control valve 233-1 of theelectric brake system 2 according to the second embodiment of thepresent disclosure may be configured with a check valve that allows onlyan oil flow in a direction from the second pressure chamber 113 to thehydraulic control unit 200 and blocks an oil flow in a reversedirection. That is, the third control valve 233-1 may allow thehydraulic pressure of the second pressure chamber 113 to be delivered tothe hydraulic control unit 200 and also prevent the hydraulic pressureof the hydraulic control unit 200 from leaking into the second pressurechamber 113 through the fourth hydraulic flow path 214.

FIG. 14 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system 3 according to a third embodiment of thepresent disclosure.

Comparing FIG. 13 with FIG. 14, the electric brake system 3 according tothe third embodiment of the present disclosure may further include asixth hydraulic flow path 216 that directly communicates the secondhydraulic flow path 212 with the fourth hydraulic flow path 214.

In the electric brake system 2 according to the second embodiment of thepresent disclosure shown in FIG. 13, a connection of the secondhydraulic flow path 212 and the fourth hydraulic flow path 214 shouldpass the third hydraulic flow path 213 at which the second control valve232 is installed, or the fifth hydraulic flow path 215 at which thecircuit balance valve 250 is provided.

However, in the electric brake system 3 according to the thirdembodiment of the present disclosure shown in FIG. 14, the secondhydraulic flow path 212 and the fourth hydraulic flow path 214 may bedirectly connected to each other through the sixth hydraulic flow path216.

Further, a fourth control valve 234 may be installed at the sixthhydraulic flow path 216. The fourth control valve 234 may be configuredwith a check valve that allows only an oil flow in a direction from thefirst pressure chamber 112 to the hydraulic control unit 200 and blocksan oil flow in a reverse direction. That is, the fourth control valve234 may allow the hydraulic pressure of the first pressure chamber 112to be delivered to the hydraulic control unit 200 and also prevent thehydraulic pressure of the hydraulic control unit 200 from leaking intothe first pressure chamber 112 through the sixth hydraulic flow path216.

FIG. 15 is a hydraulic circuit diagram illustrating a non-braking stateof an electric brake system 4 according to a fourth embodiment of thepresent disclosure.

Comparing FIG. 1 with FIG. 15, the electric brake system 4 according tothe fourth embodiment of the present disclosure may further include aseventh hydraulic flow path 217 communicating the second hydraulic flowpath 212 with the fifth hydraulic flow path 215 (that is, 215-1 and215-2). Further, the fourth hydraulic flow path 214 may communicate withthe seventh hydraulic flow path 217.

Also, a second control valve 232-1 may be configured with a check valvethat allows only an oil flow in a direction from the first pressurechamber 112 to the hydraulic control unit 200 and blocks an oil flow ina reverse direction. That is, the second control valve 232-1 may allowthe hydraulic pressure of the first pressure chamber 112 to be deliveredto the hydraulic control unit 200 and also prevent the hydraulicpressure of the hydraulic control unit 200 from leaking into the firstpressure chamber 112 through the third hydraulic flow path 213.

Further, a third control valve 233-1 may be configured with a checkvalve that allows only an oil flow in a direction from the secondpressure chamber 113 to the hydraulic control unit 200 and blocks an oilflow in a reverse direction. That is, the third control valve 233-1 mayallow the hydraulic pressure of the second pressure chamber 113 to bedelivered to the hydraulic control unit 200 and also prevent thehydraulic pressure of the hydraulic control unit 200 from leaking intothe second pressure chamber 113 through the fourth hydraulic flow path214.

Further, a fifth control valve 235 may be installed at the seventhhydraulic flow path 217. The fifth control valve 235 may be configuredwith a solenoid valve capable of bidirectionally controlling an oil flowof the seventh hydraulic flow path 217. That is, the fifth control valve235 may allow the hydraulic pressure of the first pressure chamber 112to be delivered to the hydraulic control unit 200 when a brakingoperation is performed, whereas it may allow the hydraulic pressure ofthe hydraulic control unit 200 to be delivered to the first pressurechamber 112 through the seventh hydraulic flow path 217.

Also, the fifth control valve 235 may be configured with a normallyclosed type solenoid valve that is usually closed and is open when anopening signal is received from the ECU.

Also, the fifth hydraulic flow path 215-1, which is located at a rightside in the drawing based on a point at which the fifth hydraulic flowpath 215 and the seventh hydraulic flow path 217 are connected to eachother, may be connected to the second hydraulic flow path 212, and afirst circuit balance valve 250-1 may be installed between the point anda position at which the fifth hydraulic flow path 215-1 is connected tothe second hydraulic flow path 212.

The fifth hydraulic flow path 215-2, which is located at a left side inthe drawing, is connected to the third hydraulic flow path 213, and asecond circuit balance valve 250-2 may be installed between the pointand a position at which the fifth hydraulic flow path 215-2 is connectedto the third hydraulic flow path 213.

Further, the first and second circuit balance valves 250-1 and 250-2 maybe configured with solenoid valves capable of bidirectionallycontrolling oil flows of the fifth hydraulic flow paths 215-1 and 215-2,respectively. That is, the first circuit balance valve 250-1 may allowthe hydraulic pressure of the second hydraulic flow path 212 to bedelivered to the seventh hydraulic flow path 217, and also the hydraulicpressure of the seventh hydraulic flow path 217 to be delivered to thesecond hydraulic flow path 212. Further, the second circuit balancevalve 250-2 may allow the hydraulic pressure of the third hydraulic flowpath 213 to be delivered to the seventh hydraulic flow path 217, andalso the hydraulic pressure of the seventh hydraulic flow path 217 to bedelivered to the third hydraulic flow path 213.

Also, first and second circuit balance valves 250-1 and 250-2 may beconfigured with normally closed type solenoid valves that are usuallyclosed and are open when an opening signal is received from the ECU.

As is apparent from the above description, the electric brake systemaccording to the embodiments of the present disclosure is capable ofmore rapidly providing hydraulic pressure and more precisely controllingan increase of pressure by providing a plurality of pistons of ahydraulic pressure supply device to configure a double action structure.

Also, hydraulic pressure or negative pressure may be provided bydividing a section into a low pressure section and a high pressuresection so that a braking force may be adaptively provided or releasedaccording to a braking situation.

In addition, using the high pressure section, a braking force may beprovided with a pressure greater than a maximum pressure in the lowpressure section.

[Description of Reference Numerals]  10: Brake Pedal  11: PedalDisplacement Sensor  20: Master Cylinder  30: Reservoir  40: WheelCylinder  50: Simulation Device  54: Simulator Valve  60: InspectionValve 100: Hydraulic Pressure Supply 110: Hydraulic Pressure SupplyDevice Unit 120: Motor 130: Power Conversion Unit 200: Hydraulic ControlUnit 201: First Hydraulic Circuit 202: Second Hydraulic Circuit 211:First Hydraulic Flow Path 212: Second Hydraulic Flow Path 213: ThirdHydraulic Flow Path 214: Fourth Hydraulic Flow Path 215: Fifth HydraulicFlow Path 221: Inlet Valves 222: Outlet Valves 223: Check Valve 231:First Control Valve 232: Second Control Valve 233: Third Control Valve250: Circuit Balance Valve 241: First Dump Valve 242: Second Dump Valve251: First Backup Flow Path 252: Second Backup Flow Path 261: First CutValve 262: Second Cut Valve

What is claimed is:
 1. An electric brake system comprising: a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output corresponding to displacement of a brake pedal, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to the one or more wheel cylinders; a first hydraulic flow path configured to communicate with the first pressure chamber; a second hydraulic flow path configured to branch from the first hydraulic flow path; a third hydraulic flow path configured to branch from the first hydraulic flow path; a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path; a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path; a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively; and a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively.
 2. The electric brake system of claim 1, further comprising: a first control valve provided at the second hydraulic flow path and configured to control an oil flow; a second control valve provided at the third hydraulic flow path and configured to control an oil flow; a third control valve provided at the fourth hydraulic flow path and configured to control an oil flow; and a circuit balance valve provided at the fifth hydraulic flow path and configured to control an oil flow.
 3. The electric brake system of claim 2, wherein the first control valve is configured with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction, and the second and third control valves and the circuit balance valve are configured with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.
 4. The electric brake system of claim 2, wherein the first and third control valves are configured with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction, and the second control valve and the circuit balance valve are configured with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.
 5. The electric brake system of claim 3, wherein the second and third control valves are normally closed type valves that are usually closed and are open when an opening signal is received.
 6. The electric brake system of claim 3, wherein the circuit balance valve is a normally closed type valve that is usually closed and is open when an opening signal is received.
 7. The electric brake system of claim 3, further comprising: a sixth hydraulic flow path configured to communicate the second hydraulic flow path with the fourth hydraulic flow path; and a fourth control valve provided at the sixth hydraulic flow path and configured to control an oil flow.
 8. The electric brake system of claim 7, wherein the fourth control valve is provided with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction.
 9. The electric brake system of claim 3, further comprising: a seventh hydraulic flow path configured to communicate the second hydraulic flow path with the fifth hydraulic flow path; and a fifth control valve provided at the seventh hydraulic flow path and configured to control an oil flow.
 10. The electric brake system of claim 9, wherein the fifth control valve is provided with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.
 11. The electric brake system of claim 10, wherein the fifth control valve is a normally closed type valve that is usually closed and is open when an opening signal is received.
 12. The electric brake system of claim 10, wherein the circuit balance valve is installed at the fifth hydraulic flow path between a position at which the fifth hydraulic flow path is connected to the second hydraulic flow path and a position at which the fifth hydraulic flow path and the seventh hydraulic flow path are connected to each other, and between a position at which the fifth hydraulic flow path is connected to the third hydraulic flow path and the position at which the fifth hydraulic flow path and the seventh hydraulic flow path are connected to each other, based on a position at which the seventh hydraulic flow path is connected to the fifth hydraulic flow path.
 13. The electric brake system of claim 1, further comprising: a first dump flow path configured to communicate with the first pressure chamber and connected to a reservoir; a second dump flow path configured to communicate with the second pressure chamber and connected to the reservoir; a first dump valve provided at the first dump flow path, configured to control an oil flow, and configured with a check valve configured to allow an oil flow in a direction from the reservoir toward the first pressure chamber and block an oil flow in a reverse direction; a second dump valve provided at the second dump flow path, configured to control an oil flow, and configured with a check valve configured to allow an oil flow in a direction from the reservoir toward the second pressure chamber and block an oil flow in a reverse direction; and a third dump valve provided at a bypass flow path connecting an upstream side of the second dump valve to a downstream side thereof at the second dump flow path, configured to control an oil flow, and configured with a solenoid valve configured to control an oil flow between the reservoir and the second pressure chamber bidirectionally.
 14. The electric brake system of claim 13, wherein the third dump valve is a normally opened type valve that is usually opened and is closed when a closing signal is received.
 15. The electric brake system of claim 1, wherein the hydraulic pressure supply device further includes: the cylinder block; the piston movably accommodated inside the cylinder block and configured to perform reciprocal movement by means of a rotational force of a motor; a first communicating hole formed at the cylinder block forming the first pressure chamber and configured to communicate with the first hydraulic flow path; and a second communicating hole formed at the cylinder block forming the second pressure chamber and configured to communicate with the fourth hydraulic flow path.
 16. An electric brake system comprising: a master cylinder at which first and second hydraulic ports are formed, connected to a reservoir storing oil therein, configured with one or more pistons, and configured to discharge oil according to a pedal effort of a brake pedal; a pedal displacement sensor configured to sense displacement of the brake pedal; a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output from the pedal displacement sensor, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to one or more wheel cylinders; a first hydraulic flow path configured to communicate with the first pressure chamber; a second hydraulic flow path configured to branch from the first hydraulic flow path; a third hydraulic flow path configured to branch from the first hydraulic flow path; a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path; a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path; a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively, and first and second inlet valves configured to control the first and second branching flow paths, respectively; a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively; a first backup flow path configured to connect the first hydraulic port to the second hydraulic flow path; a second backup flow path configured to connect the second hydraulic port to the third hydraulic flow path; a first cut valve provided at the first backup flow path and configured to control an oil flow; a second cut valve provided at the second backup flow path and configured to control an oil flow; and a simulation device provided at a flow path branching from the first backup flow path, configured with a simulator valve provided at a flow path connecting a simulation chamber storing oil therein to the reservoir, and configured to provide a reaction force according to a pedal effort of the brake pedal.
 17. The electric brake system of claim 16, further comprising: a first control valve provided at the second hydraulic flow path and configured to control an oil flow; a second control valve provided at the third hydraulic flow path and configured to control an oil flow; a third control valve provided at the fourth hydraulic flow path and configured to control an oil flow; and a circuit balance valve provided at the fifth hydraulic flow path and configured to control an oil flow.
 18. The electric brake system of claim 17, wherein the first backup flow path is connected to a downstream side of the first control valve at the second hydraulic flow path, and the second backup flow path is connected to a downstream side of the second control valve at the third hydraulic flow path.
 19. The electric brake system of claim 18, further comprising an electronic control unit (ECU) configured to control an operation of the motor, and opening and closing of the second and third control valves, the circuit balance valve, and first to fourth inlet valves on the basis of hydraulic pressure information and displacement information of the brake pedal.
 20. The electric brake system of claim 19, wherein, when an imbalance in pressure between the first pressure chamber and the second pressure chamber occurs, the ECU opens the second control valve and the third control valve to accomplish a balance in pressure between the first pressure chamber and the second pressure chamber. 